1. Field of the Invention
This invention is related in general to the fields of immobilization of both inorganic and organic (including biological) materials on solid surfaces and the detection of their functional interactions. In particular, the invention provides a new method for immobilization of biological molecules on solid supports while providing a biocompatible environment, so that these materials may be detected in a native-like state using various well-known techniques and devices.
2. Description of the Related Art
For the detection of a material using any technique or device two goals should be met. First, the material should be immobilized in an effective manner such that accurate detection is possible. Second, the immobilized material should be able to be observed in a state that best approximates its native or in vivo condition. This is particularly important for biological materials where their in vivo conformation is crucial to both their quantitative and qualitative interactions with other molecules. Detection of any material utilizing available techniques and devices requires that the material be deposited on a solid surface. The conventional techniques for the immobilization of materials (including biological materials) on solid surfaces utilize any of the following methods:
(a) vacuum deposition; PA1 (b) adsorption from solvents; and PA1 (c) physico-chemical and mechanical entrapment using different kinds of membrane systems.
The present invention utilizes a novel variant of the physico-chemical and mechanical entrapment method using a self-assembling membrane system. Specifically, it uses a self-assembled bilayer, which resembles a freely suspended lipid bilayer membrane, deposited on a solid support. This bilayer membrane provides the means for the immobilization of the material to be examined. Prior techniques utilizing bilayers for entrapment of the target material have been formed by the Langmuir-Blodgett technique. This technique produces a monomolecular Langmuir-Blodgett film. This film has a compressed surface layer of molecules that are amphiphilic (i.e. they have polar ends that readily interact with an aqueous solution and nonpolar ends that do not), thus their alignment is highly regularized and dense. The dense structure of the Langmuir-Blodgett film incorporates less fluid and behaves more like a rigid semi-solid structure. As a result, any material incorporated into this film is less mobile. For organic (i.e. biological materials) this means that they are less able to freely interact with one another and hence they behave less as they would in their native (in vivo) environment. If one is examining the interaction between various molecules this limitation can be a great detriment to any detection device utilizing a Langmuir-Blodgett film.
Unlike a Langmuir-Blodgett film, a self-assembled, freely suspended lipid bilayer behaves more like the lipid bilayer membranes found in vivo in cells. Another important feature of the freely suspended bilayer membranes is that solvent molecules are involved in their formation and therefore can be experimentally manipulated. This type of manipulation is not possible with Langmuir-Blodgett films. In spite of their advantages, freely suspended lipid bilayers have several disadvantages, their extreme fragility and size. This fragility and tendency to form small structures (usually less than 1 mm in diameter) makes it difficult to utilize the bilayers in any of the current analytical systems. If membranes composed of freely suspended lipid bilayers could be formed uniformly on a planar surface, they would be able to be utilized in a variety of currently available analytical techniques. The present application is directed to a method of forming these self-assembled freely suspended lipid bilayers deposited on planar solid surfaces such that they cover a relatively large area yet retain the desirable characteristics mentioned above.